Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

Expandable-polymer-particle material comprising at least one
thermoplastic polyurethane (TPU) with Vicat softening point (in
accordance with ISO 306/ASO) below 80° C. and from 5 to 95% by
weight of at least one polymer obtainable via free-radical
polymerization, based on the entirety of TPU and of the polymer
obtainable via free-radical polymerization, where the polymer obtainable
via free-radical polymerization has been bonded to the TPU in a manner
that gives a comb polymer, graft polymer, or copolymer, is suitable for
the production of moldings, in particular for use as insulation material.

Claims:

1.-18. (canceled)

19. An expandable-polymer-particle material comprising at least one
thermoplastic polyurethane (TPU) with Vicat softening point below
80.degree. C., in accordance with ISO 306/ASO, and 5 to 95% by weight of
at least one polymer that is obtained by free-radical polymerization, the
percent by weight based on the entirety of TPU and the at least one
polymer, wherein the at least one polymer obtained by free radical
polymerization is bonded to the TPU to provide a comb polymer, a graft
polymer, or a copolymer.

20. The expandable-polymer-particle material according to claim 19,
wherein the at least one polymer is a styrene polymer.

21. The expandable-polymer-particle material according to claim 20,
wherein the styrene polymer is polystyrene.

22. The expandable-polymer-particle material according to claim 19,
wherein the Vicat softening point is in a range of 60 to 75.degree. C.

23. The expandable-polymer-particle material according to claim 19,
wherein the TPU has a Shore hardness in a range of 50 to 150.

24. The expandable-polymer-particle material according to claim 19,
wherein the TPU has a glass transition temperature in a range of -20 to
-60.degree. C.

25. The expandable-polymer-particle material according to claim 19,
wherein the TPU is prepared from diphenylmethane 2,2-diisocyanate,
polytetrahydrofurans, and 1,4-butenediol.

26. The expandable-polymer-particle material according to claim 25,
wherein the polytetrahydrofurans are selected from polytetrahydrofuran
1000 or polytetrahydrofuran 2000.

27. A process for the production of an expandable-polymer-particle
material, the process comprising the following steps: a) providing an
aqueous dispersion comprising; one or more TPUs with Vicat softening
point below 80.degree. C., in accordance with ISO 306/ASO, 5 to 95% by
weight of one or more monomers that can be polymerized by free-radical
polymerization, the percent by weight based on the entirety of TPU and
the one or more monomers, a polymerization initiator, a dispersing agent,
and optionally additional substances and/or polymerization aids, wherein
the aqueous dispersion is at a temperature at which substantial
polymerization of the one or more monomers does not occur; b) optional
stirring the aqueous dispersion for 1 to 24 hours at a temperature at
which substantial polymerization of the one or more monomers does not
occur; c) polymerizing the one or more monomers by free-radical
polymerization to provide an aqueous suspension including a comb polymer,
a graft polymer, or a copolymer, in conjunction with the TPU; and d)
adding a physical blowing agent to the aqueous suspension.

28. The process according to claim 27, wherein the free-radical
polymerization is carried out in the presence of a brominated organic, a
phosphorus-containing flame retardant, and/or organic peroxides.

29. The process according to claim 27, wherein the free-radical
polymerization is carried out in the presence of a crosslinking agent.

30. The process according to claim 27 wherein at the temperature at which
substantial polymerization of the one or more monomers does not occur,
the TPU is swollen in the aqueous dispersion of the one or more monomers,
the polymerization initiator, and the optional additional substances or
the polymerization aids.

31. The process according to claim 30, wherein the polymerization
temperature of the one or more monomers is from 110 to 140.degree. C.,
and the temperature at which substantial polymerization of the one or
more monomers does not occur is from 10 to 60.degree. C.

32. The process according to claim 27, wherein the blowing agent is added
to the suspension at a temperature above 100.degree. C.

33. The process according to claim 27, wherein the aqueous suspension
further comprises a Pickering stabilizer in combination with a surfactant
and/or a protective colloid.

34. A foam molding obtainable from expanded-polymer-particle material
according to claim 19.

35. A floorcovering, insulation material, or in shoe sole or bumper
comprising a foam molding according to claim 34.

Description:

[0001] The invention relates to expandable-polymer-particle material based
on thermoplastic polyurethanes (TPUs) comprising a styrene polymer and
TPU, to a process for the production thereof, to moldings obtainable from
the polymer-particle material, and also to use thereof as elastomeric
foam.

[0002] Foams based on styrene polymers have been known for some time and
are widely used by way of example for the production of insulation
materials. Alongside the major advantages of these materials, for example
in relation to insulation properties, low density, water resistance, and
expandability, there are disadvantages in respect of chemicals resistance
and impact resistance.

[0003] Thermoplastic polyurethanes in foamed form are also known. Examples
of their features are excellent resilience, transparency, abrasion
resistance, and chemicals resistance, but they have disadvantages such as
inadequate dimensional stability and unsatisfactory foamability: it is
technically very difficult to produce an expandable moldable foam from
TPU, because physical blowing agents such as pentane are very rapidly
lost into the environment from TPU via diffusion (poor blowing-agent
retention capability). Physical blowing agents in straight TPU cannot
moreover generate sufficient foaming pressure, and it is therefore not
possible to use an EPS prefoamer for expansion of straight TPU comprising
blowing agent.

[0004] Attempts have also been made to combine the advantageous properties
of foams based on polystyrene and foams based on TPU.

[0005] The application WO 2007/082838 describes by way of example the
production of expandable TPUs via compounding of TPU with a blowing agent
in extrusion-based processes.

[0007] JP-A 1980-080440 describes a process for the production of
expandable-polymer-particle material where from 20 to 80% by weight of
TPU-elastomer-particle material and from 80 to 20% by weight of a monomer
or methacrylate ester are suspended in an aqueous medium and polymerized.

[0008] JP-A 2007-231068 discloses styrene-modified expandable-TPU-particle
material comprising 100 parts by weight of TPU and from 20 to 300 parts
by weight of a styrene polymer, where styrene polymer particles of size
0.5 μm or less have been dispersed in the TPU.

[0009] Although good results are already being achieved with the known
materials, there remains nevertheless much room for improvement, for
example in relation to blowing-agent-retention capability combined with
high resilience of these materials.

[0010] It was therefore an object to develop TPU-based materials which in
particular can retain a physical blowing agent (pentane) over a period of
weeks, can be processed in commercially available EPS machines, and
nevertheless still have a sufficient level of elastomeric properties.

[0011] It has been found possible to produce polymers with the desired
advantageous properties from TPU and from a polymer obtainable via
free-radical polymerization, if the TPU used has a Vicat softening point
below 80° C. (in accordance with ISO 306/A50) and the polymer
obtainable via free-radical polymerization has been bonded in the form of
comb polymer, graft polymer, or copolymer to the TPU.

[0012] The invention therefore provides expandable-polymer-particle
material comprising at least one thermoplastic polyurethane (TPU) with
Vicat softening point (in accordance with ISO 306/A50) below 80°
C. and from 5 to 95% by weight, based on the entirety of TPU and of
polymer obtainable via free-radical polymerization, of at least one
polymer obtainable via free-radical polymerization, where the polymer
obtainable via free-radical polymerization has been bonded to the TPU in
a manner that gives a comb polymer, graft polymer, or copolymer.

[0013] The invention further provides expanded-polymer-particle material
of the invention, obtainable via prefoaming of the polymer-particle
material of the invention.

[0014] The invention also provides foam moldings obtainable from the
prefoamed polymer-particle material of the invention.

[0015] The invention further provides a process for the production of the
polymer-particle material of the invention, comprising the following
steps:

[0016] a) dispersion of one or more TPUs with Vicat softening
point below 80° C., from 5 to 95% by weight of one or more
monomers polymerizable by a free-radical route and optionally comonomers,
based on the entirety of TPU and of the monomers mentioned, of a
polymerization initiator, of a dispersing agent, and optionally of other
additional substances and/or polymerization aids in an aqueous medium at
a temperature at which no substantial polymerization of the styrene
monomers takes place;

[0017] b) optional stirring of the resultant
dispersion for from one to 24 h at a temperature at which no substantial
polymerization of the monomers polymerizable by a free-radical route
takes place;

[0018] c) polymerization of the monomers polymerizable by a
free-radical route in the form of a comb polymer, graft polymer or
copolymer onto the TPU, and

[0019] d) addition of a physical blowing
agent to the aqueous suspension.

[0020] The invention also provides the use of the foam moldings of the
invention as elastomeric foam, preferably as insulation material for
facades, interiors of residential buildings, and/or
solid-borne-sound-deadening, for sports floors, shoe soles, and/or
bumpers for automobiles.

[0021] Thermoplastic polyurethanes (TPUs) and process for production
thereof are known.

[0023] Vicat softening point is determined here in accordance with ISO 306
by the ASO method, i.e. using a force of 10 N and a heating rate of
50° C./h.

[0024] Vicat softening point is determined on specimens which are free
from blowing agent and which comprise none of the additives
conventionally used for the desired applications.

[0025] A Vicat softening point of the invention can be achieved by methods
known to the person skilled in the art, for example via use of
appropriate monomer units in the production of the TPU (see below).

[0026] The Shore A hardness of TPU grades used in the invention is
preferably in the range from 50 to 150, particularly preferably from 65
to 85 (measured in accordance with DIN 53505).

[0027] The melting range (glass transition) is preferably in the range
from -20° C. to -60° C.

[0028] Elongation at break in accordance with DIN 53504-S2 is preferably
>550%.

[0029] In another feature essential to the invention, alongside the stated
Vicat softening point, TPUs used in the invention must comprise
functional groups which, under the typical conditions of free-radical
polymerization of, for example, styrene (T=from 100-140° C.; from
0.1-3% by weight of peroxide initiator, such as dicumyl peroxide) form a
comb polymer, graft polymer, or copolymer with the monomers capable of
free-radical polymerization. A first variant achieves this via use of a
di- or monoisocyanate component having hydrogen atoms that are
extractable by a free-radical route, an example being diphenylmethane
4,4'-, 2,4'-, and/or 2,2'-diisocyanate (MDI). or else a mixture of these,
during the production of the TPUs in a manner (see below) that is in
principle known.

[0030] In a second variant, monomers that are capable of free-radical
polymerization and that have groups (alcohol groups, epoxy groups, amine
groups) which can enter into a polyaddition reaction with isocyanates are
added during the production of the TPUs in a known manner (see below).
Particular preference is given here to the following compounds as
monomers: hydroxyethyl methacrylate; 1,2- and 1,3-dihydroxypropyl
methacrylate; glycidyl methacrylate, ortho-, meta-, and
para-hydroxystyrene, meta- and para-aminostyrene, methacrylamide,
1,4-butenediol, 1,4-butynediol, and/or polybutadienediol.

[0032] All molar masses in this specification stated in [kg/mol] are the
number-average molar mass.

[0033] Preferred embodiments produce TPU via reaction from a mixture of
isocyanates (a) with compounds (b) which are reactive toward isocyanates
and which preferably have a molar mass of from 0.5 kg/mol to 10 kg/mol,
and optionally with chain extenders (c) which preferably have a molar
mass of from 0.05 kg/mol to 0.5 kg/mol.

[0034] In other preferred embodiments, at least one chain regulator (c1),
one catalyst (d), and optionally at least one filler, auxiliary, and/or
additional substance is also added to the mixture for the production of
TPU. The substance groups designated by small letters, sometimes also by
numerals, are also termed components.

[0035] The components (a), (b), (c), (c1), (d), and (e) usually used in
the production of the TPUs are described by way of example hereinafter,
and comprise the following substance groups: isocyanates (a), compounds
(b) reactive toward isocyanates, chain extenders (c), chain regulators
(c1), catalysts (d), and/or at least one conventional filler, auxiliary,
and/or additional substance.

[0036] In all cases, production of TPUs requires a mixture of isocyanates
(a) and compounds (b) reactive toward isocyanates. The further addition
of components (c), (c1), (d), and (e) is optional, and can be implemented
singly or in any of the possible variations. The term component here in
each case means an individual substance or a mixture of the substances of
that component.

[0037] The term structural components is used for the following
components: isocyanates (a), compounds (b) reactive toward isocyanates,
and chain extenders (c) and, if used, also the chain regulators (c1).

[0039] Particular preference is given to diphenylmethane 4,4'-, 2,4'-, and
2,2'-diisocyanate (MDI), and also to mixtures of these. Subordinate
amounts, e.g. amounts of up to 3 mol %, preferably of up to 1 mol %,
based on the organic diisocyanate, of a polyisocyanate of functionality
three or higher can optionally replace the organic diisocyanates, but the
amount of this replacement must be restricted so that polyurethanes
obtained are still thermoplastically processable. A relatively large
amount of these more than difunctional isocyanates is advantageously
compensated by concomitant use of less than difunctional compounds having
reactive hydrogen atoms, in order to avoid any excessive chemical
crosslinking of the polyurethane.

[0040] In preferred embodiments, compounds (b) used that are reactive
toward isocyanates are polyetherols, polyesterols, and/or
polycarbonatediols, another collective term usually used for these being
"polyols".

[0041] TPU is preferably produced from polyether alcohol, and it is
particularly preferable to use polyetherdiol.

[0042] Suitable polyetherdiols can be produced by known processes, for
example via anionic polymerization of alkylene oxides with alkali metal
hydroxides, such as sodium hydroxide or potassium hydroxide, or with
alkali metal alcoholates, such as sodium methoxide, sodium ethoxide, or
potassium ethoxide, or potassium isopropoxide, as catalysts, and with
addition of at least one starter molecule which comprises from 2 to 3,
preferably 2, reactive hydrogen atoms in bonded form, or via cationic
polymerization with Lewis acids as catalysts from one or more alkylene
oxides having from 2 to 4 carbon atoms in the alkylene moiety. Examples
of suitable alkylene oxides are tetrahydrofuran, propylene 1,3-oxide, and
particularly preferably ethylene oxide and propylene 1,2-oxide. The
alkylene oxides can be used individually, in alternating succession, or
in the form of mixtures. Examples of starter molecules that can be used
are: water, organic dicarboxylic acids, such as succinic acid and adipic
acid, and preferably dihydric alcohols optionally comprising ether
bridges in bonded form, e.g. ethanediol, 1,2-propanediol, 1,4-butanediol,
diethylene glycol, 1,6-hexanediol, and 2-methyl-1,5-pentanediol. The
starter molecules can be used individually or in the form of mixtures.
The polytetrahydrofurans (PTHFs) comprising hydroxy groups are in
particular suitable and preferred.

[0043] The average molecular weights of the polyetherols, where these are
in essence linear, are usually from 500 to 8000, preferably from 600 to
6000, and the preferred average molecular weight of the PTHF here is from
500 to 2500, in particular from 800 to 2000. The materials here can be
used either individually or else in the form of mixtures with one
another.

[0044] A particularly preferred polyetherdiol is polytetrahydrofuran. It
is preferable that the molar masses of the polyether alcohols and
polytetrahydrofuran used are from 0.6 kg/mol to 2.5 kg/mol. The polyether
alcohols are used individually or else in the form of a mixture of
various polyether alcohols.

[0045] In alternative embodiments, TPU is produced from polyester alcohol.
In one preferred embodiment, polyesterdiol is used for this purpose. A
preferred polyesterdiol is produced from adipic acid and 1,4-butanediol.
Preferred embodiments of the polyester alcohols have a molar mass of from
0.6 kg/mol to 2.5 kg/mol.

[0046] In embodiments to which further preference is given, said polyols
have molar masses of from 0.5 kg/mol to 8 kg/mol, preferably from 0.6
kg/mol to 6 kg/mol, in particular from 0.8 kg/mol to 4 kg/mol, and in
embodiments to which further preference is given they have an average
functionality of from 1.8 to 2.3, more preferably from 1.9 to 2.2, in
particular 2. In one particularly preferred embodiment, the polyol is a
polyester alcohol, preferably synthesized from polytetrahydrofuran, and
in an embodiment to which further preference is given its molar mass is
from 0.6 kg/mol to 2.5 kg/mol.

[0047] In preferred embodiments, chain extenders (c) used comprise
aliphatic, araliphatic, aromatic and/or cycloaliphatic compounds, and in
embodiments to which further preference is given the molar mass of these
is from 0.05 kg/mol to 0.5 kg/mol. In some preferred embodiments, chain
extenders (c) are compounds having two functional groups, for example
diamines and/or alkanediols having from 2 to 10 carbon atoms in the
alkylene moiety, in particular 1,4-butanediol, 1,6-hexanediol, and/or
di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona-, and/or
decaalkylene glycols having from 3 to 8 carbon atoms, and corresponding
oligo- and/or polypropylene glycols. In other embodiments, mixtures of
the chain extenders are used for the production of TPU.

[0048] In some embodiments, chain regulators (c1) are used, usually with a
molar mass of from 0.03 kg/mol to 0.5 kg/mol. Chain regulators are
compounds which have only one functional group with regard to
isocyanates. Examples of chain regulators are monohydric alcohols,
monofunctional amines, preferably methylamine, and/or monohydric polyols.
Chain regulators can be used for controlled adjustment of the flow
behavior of the mixtures of the individual components. In preferred
embodiments, the amount used of chain regulators is from 0 parts by
weight to 5 parts by weight, more preferably from 0.1 part by weight to 1
part by weight, based on 100 parts by weight of the compound b) reactive
toward isocyanates. Chain regulators are used to supplement chain
extenders or in place thereof.

[0049] In other embodiments, the TPU production process uses at least one
catalyst (d) which in particular accelerates the reaction between the NCO
groups of the diisocyanates (a) and the compounds reactive toward
isocyanates, preferably hydroxy groups of structural components (b), (c),
and (c1). In preferred embodiments, the catalyst is one selected from the
group of the tertiary amines, such as triethylamine,
dimethylcyclohexylamine, N-methylmorpholine, N,N'-dimethylpiperazine,
2-(dimethylaminoethoxy)ethanol, diazabicyclo[2.2.2]octane, and similar
substances. In embodiments to which further preference is given, the at
least one catalyst is one selected from the group of the organometallic
compounds and by way of example is titanic ester, an iron compound, such
as iron(III) acetylacetonate, a tin compound, such as tin diacetate, tin
dioctanoate, tin dilaurate, or a dialkyltin salt of an aliphatic
carboxylic acid, e.g. dibutyltin diacetate, dibutyltin dilaurate, or the
like.

[0050] In some embodiments, the catalysts are used individually, and in
other embodiments mixtures of catalysts are used. In preferred
embodiments, the amounts used of the catalyst or of the mixture of
catalysts are from 0.0001 part by weight to 0.1 part by weight per 100
parts by weight of the compound (b) reactive toward isocyanates,
preferably polyhydroxy compound.

[0051] Examples that may be mentioned of auxiliary and/or additive (e) are
hydrolysis stabilizers and flame retardants. Other additives and
auxiliaries can be found in standard works, such as the Becker and Braun
(1996) work mentioned above.

[0052] Other substances that can be added to structural components (a) to
(c), and optionally (c1), alongside catalysts (d), or else without the
use of catalysts, are hydrolysis stabilizers, such as polymeric and
low-molecular-weight carbodiimides.

[0053] The molar ratios of structural components (b) and (c) can be varied
relatively widely in order to adjust the Shore hardness of TPU. In
preferred embodiments, the molar ratio of component (b) to the entire
amount of chain extenders (c) used is from 10:1 to 1:10, preferably from
5:1 to 1:8, more preferably from 1:1 to 1:4, where the hardness of TPU
rises with increasing content of chain extender (c). This method permits
adjustment to Shore hardness values of from A44 to D80, particularly
preferred Shore hardness values being from A44 to A84. The Shore hardness
values are determined in accordance with DIN 53505.

[0054] In embodiments to which further preference is given, the reaction
to give TPU takes place with customary indices. The index is defined via
the ratio of the entirety of isocyanate groups used during the reaction
in component (a) to the groups reactive toward isocyanates, i.e. the
active hydrogen atoms, in components (b) and (c). If the index is 100,
there is one active hydrogen atom, i.e. one function reactive toward
isocyanates, in components (b) and (c) for each isocyanate group in
component (a). If indices are above 100, there are more isocyanate groups
present than groups reactive toward isocyanates, for example OH groups.

[0055] In particularly preferred embodiments, the reaction to give TPU
takes place with an index of from 60 to 120, more preferably with an
index of from 80 to 110.

[0056] The production of TPU is preferably carried out by one of the known
processes addressed below. Preferred embodiments are the continuous
process, for example using reaction extruders, the belt process, the
"one-shot" process, or the prepolymer process. The batch process and the
prepolymer process are embodiments to which preference is equally given.
In these processes, reactive components (a) and (b), and also optionally
(c), (c1), (d), and/or (e) can be mixed with one another in succession or
simultaneously, whereupon the reaction of components (a) and (b)
immediately begins.

[0057] In the extruder process, structural components (a) and (b), and
also optionally components (c), (c1), (d), and/or (e) are introduced
individually or in the form of a mixture into the extruder and by way of
example are reacted at temperatures of from 100° C. to 280°
C., preferably from 140° C. to 250° C. The resultant TPU is
extruded, cooled, and pelletized. It can sometimes be advantageous to
condition the resultant TPU prior to further processing at from
80° C. to 120° C., preferably at from 100° C. to
110° C., for a period of from 1 to 24 hours, i.e. to permit the
mixture to continue reacting at constant temperature.

[0058] Preferred types of TPU have a relatively large content of the soft
phase in comparison with the hard phase, preferred amounts of soft phase
being from 5 to 30% by weight, particularly preferably from 10 to 25% by
weight. It is moreover preferable that the nitrogen content of the hard
phase is relatively high.

[0059] Examples of preferred types of TPU are available commercially as
Elastollan®1170 AU, Elastollan®1180, Elastollan® 1175 A
10W000, and Elastollan®880 A 13N000 from BASF Polyurethan GmbH,
Lemforde, Germany.

[0060] Particular preference is given to Elastollan® 1170 AU, a TPU
that is obtainable from polytetrahydrofuran 1000 and 2000 (where the
numerals relate to the molecular weight Mw, and the products are by
way of example available commercially from BASF SE), and from a small
proportion of 1,4-butanediol and diphenylmethane 4,4'-diisocyanate (MDI).

[0061] The polymer-particle material of the invention comprises, alongside
the TPU, from 5 to 95% by weight (based on the entirety of TPU and
styrene polymers) of one or more polymers obtainable via free-radical
polymerization and bonded in the form of comb polymer, graft polymer, or
copolymer to the TPU. It is preferable that the proportion of these is
from 80 to 30%, particularly preferably from 75 to 50%, very particularly
preferably from 75 to 65%.

[0064] The expression styrene polymer in the invention comprises polymers
based on styrene, or alpha-methylstyrene, or on a mixture of styrene and
alpha-methylstyrene. Styrene polymers of the invention are based on at
least 50% by weight of styrene and/or alpha-methylstyrene monomers.

[0066] The polymer-particle material of the invention features a
particular TPU phase morphology, which is composed of a continuous phase
made of TPU homopolymer and of a discontinuous phase made of the graft
polymer of TPU and of the polymer obtainable via free-radical
polymerization. The TPU phase here ideally has a phase morphology as
shown in FIG. 1 (TEM image). The graft polymer made of TPU and of the
polymer obtainable via free-radical polymerization here forms round to
elliptical discontinuous phases with a diameter of from 50 to 500 nm.
Surrounding these there is a coherent continuous TPU network. FIG. 1
provides EFTEM (energy filtered transmission electron microscopy) images
of expandable TPU-PS pellets (40:60) with good blowing-agent-retention
capability. In FIGS. 1 and 1b the contrasting agent is RuO4, and in
FIGS. 1c and 1d it is phosphotungstic acid.

[0067] By way of example, expandable bead polymers having from 50-70%
polystyrene content have a marginal zone with a diameter of from 10-100
μm composed of straight TPU (see FIG. 2). This marginal zone provides
a particular surface (with the good grip of straight TPU) to the foams
produced from the polymer, and the resultant foams therefore have a very
high-quality appearance. FIG. 2 shows SEM images of expandable TPU-PS
pellets (50:60) with good blowing-agent-retention capability: the
specimens were cryosectioned, contrasted with RuO4, and then viewed
by SEM, which was used to obtain images of examples (marginal zone A;
bead center B) of locations. Straight TPU appears paler than
styrene-modified TPU in the SEM images.

[0068] An essential element of the invention is that the polymer structure
described above can be obtained under suitable conditions via
free-radical polymerization of one or more monomers in the TPU network
swollen by said monomer(s).

[0069] In order to improve mechanical properties or resistance to
temperature change, compatibilizers can optionally be used to blend the
polymer-particle material of the invention with thermoplastic polymers
such as polyamides (PA), polyolefins such as polypropylene (PP) or
polyethylene (PE), polyacrylates such as polymethyl methacrylate (PMMA),
polycarbonates (PC), polyesters such as polyethylene terephthalate (PET)
or polybutylene terephthalate (PBT), polyether sulfones (PES), polyether
ketones, or polyether sulfides (PES), or a mixture thereof, in
proportions which are in total up to at most 30% by weight, preferably in
the range from 1 to 10% by weight, based on the polymer content. Mixtures
in the ranges of amounts mentioned are also moreover possible with, for
example, hydrophobically modified or functionalized polymers or
oligomers, rubbers such as polyacrylates or polydienes, for example
styrene-butadiene block copolymers, or biodegradable aliphatic or
aliphatic/aromatic copolyesters.

[0070] The polymer pellets of the invention comprise a blowing agent
component. The blowing agent component comprises one or more blowing
agents in a proportion of in total from 1 to 15% by weight, preferably
from 2 to 6% by weight, particularly preferably from 3 to 5% by weight,
based on. Examples of suitable blowing agents are aliphatic hydrocarbons
having from 2 to 8, preferably from 3 to 8 carbon atoms, and mixtures of
2 or more of these hydrocarbons and/or 2 or more isomers of these
hydrocarbons. Preference is given to butane isomers and pentane isomers,
for example isobutane, n-butane, isopentane, n-pentane, and mixtures of
these, in particular pentaneisomers, for example isopentane and
n-pentane, and mixtures of these isomers. The following are in particular
suitable as co-blowing agents, preferably in a proportion from 0 to 3% by
weight, preferably from 0.25 to 2.5% by weight, in particular from 0.5 to
2.0% by weight (based on (P)): (C1-C4)-carbonyl compounds, for
example ketones and esters, C1-C4-alcohols, and
C2-C4-ethers. Preferred co-blowing agents are ketones,
particularly acetone.

[0071] The stated amounts of blowing agents are the amounts added during
the production process. The content in the product and in particular
after storage is correspondingly lower.

[0072] The bulk density of the expanded polymer pellets of the invention
is generally at most 300 g/l, preferably from 15 to 200 g/l, particularly
preferably in the range from 40 to 150 g/l. When fillers are used, bulk
densities in the range from 40 to 150 g/l can arise, depending on the
nature and amount of the filler.

[0073] The polymer-particle material of the invention preferably
comprises, alongside polymer component and blowing agent component, an
additive component. Suitable additives are known to the person skilled in
the art.

[0074] In one preferred embodiment, at least one nucleating agent is added
to the polymer component (P), Examples of nucleating agents that can be
used are amounts which are generally from 0.1 to 10% by weight,
preferably from 0.1 to 3% by weight, particularly preferably from 0.1 to
1.5% by weight, based on (P), of fine-particle, inorganic solids such as
talc powder, silicon dioxide, mica, clay, zeolites, calcium carbonate,
and/or polyethylene waxes. The average particle diameter of the
nucleating agent is generally in the range from 0.01 to 100 μm,
preferably from 1 to 60 μm. A particularly preferred nucleating agent
is talc powder, for example talc powder from Luzenac Pharma. The
nucleating agent can be added by methods known to the person skilled in
the art.

[0076] It is very particularly preferable to add amounts which are
generally from 0.05 to 25% by weight, in particular amounts of from 2 to
8% by weight, based on (P), of graphite. Suitable particle sizes for the
graphite used are in the range from 1 to 50 μm, preferably in the
range from 2 to 10 μm.

[0077] The use of UV stabilizers has proven advantageous. Specifically in
the case of the polymers PS1) such as SMA, strong UV irradiation leads to
visible yellowing and to chemical changes in the material which are
attended by significant embrittlement. Reactivity, e.g. with SMA, is an
important factor for the selection of suitable UV stabilizers. While
stabilizers based on benzotriazoles such as Tinuvin 234 can improve UV
resistance without altering processing properties and foam properties,
stabilizers based on sterically hindered amines, for example Uvinul 4050
and Tinuvin 770, are less suitable for the system of materials of the
invention.

[0078] It is preferable that the pellets of the invention comprise, as
additive, a UV stabilizer based on amounts in the range from 0.05 to 5
parts by weight, preferably from 0.1 to 1 part by weight, based on 100
parts by weight of polymer P, of benzotriazoles.

[0079] Because various industries apply fire-protection regulations, it is
preferable to add one or more flame retardants. Examples of suitable
flame retardants are tetrabromobisphenol A, brominated polystyrene
oligomers, brominated butadiene-polystyrene copolymers in accordance with
WO 2007/058736, tetrabromobisphenol A diallyl ether, and
hexabromocyclododecane (HBCD), in particular the industrial products,
where these in essence comprise the α-, β-, and γ-isomer
with added synergists, such as dicumyl. Preference is given to brominated
aromatics, such as tetrabromobisphenol A, and to brominated styrene
oligomers. Examples of suitable halogen-free flame retardants are
expandable graphite, red phosphorus, and phosphorus compounds, such as
expandable graphite, red phosphorus, triphenyl phosphate, and
9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide.

[0081] Preference is moreover given to organic peroxides (dicumyl
peroxide), sulfur, and disulfides as synergists. The abovementioned flame
retardants can either be dissolved in the monomers before the
polymerization reaction starts or incorporated in the TPU by extrusion.

[0082] In one preferred embodiment, the polymer-particle material of the
invention has a coating of one or more coating components, where said
coating components can optionally have been adsorbed onto a porous solid.

[0084] Particular preference is given to the corresponding commercially
available products, which are generally mixtures of the corresponding
mono-, di-, and triesters, which also can comprise small proportions of
free glycerol and of free fatty acids, examples being glycerol
tristearates and glycerol monostearates.

[0085] It has proven particularly preferable to coat the polymer with from
0.1 to 1% by weight of hydrophilic silica (e.g. Sipernat® FK320;
Evonik).

[0086] Other possible coating materials are plasticizers from the group
consisting of a) one or more alkyl esters of cyclohexanecarboxylic acids
with boiling point ≧160° C., b) one or more phenyl
C10-C21-alkanesulfonates with boiling point ≧150°
C., and c) mixtures of components a) and b).

[0087] Preference is given to the mono-, di-, and triglycerides which are
obtainable from glycerol and stearic acid, glycerol and 12-hydroxystearic
acid, and glycerol and ricinoleic acid, and also to mixed di- and
triglycerides which are obtainable from one or two fatty acids from the
group of oleic acid, linoleic acid, linolenic acid, and palmitic acid,
alongside stearic acid, 12-hydroxystearic acid, and ricinoleic acid.

[0088] The total amount of additives is generally from 0 to 5% by weight,
preferably from 0 to 0.5% by weight, based on the total weight of the
polymers used.

[0089] The polymer-particle material of the invention is obtainable via a
process for the production of expandable-polymer-particle material,
comprising the following steps:

[0090] a) dispersion of one or more
TPUs with Vicat softening point below 80° C., from 5 to 95% by
weight of one or more monomers polymerizable by a free-radical route and
optionally comonomers, based on the entirety of TPU and of the monomers
mentioned, of a polymerization initiator, of a dispersing agent, and
optionally of other additional substances and/or polymerization aids in
an aqueous medium at a temperature at which no substantial polymerization
of the monomers polymerizable by a free-radical route takes place;

[0091] b) optional stirring of the resultant dispersion for from one to
24 h at a temperature at which no substantial polymerization of the
monomers polymerizable by a free-radical route takes place,

[0092] c)
polymerization of the monomers polymerizable by a free-radical route in
the form of a comb polymer, graft polymer or copolymer onto the TPU, and

[0093] d) addition of a physical blowing agent to the aqueous suspension.

[0094] For the suspension polymerization process of the invention it is
preferable in accordance with what has been said above to use styrene
alone. It is also possible as an alternative to use other monomers
capable of free-radical polymerization, for example alkylstyrenes,
divinylbenzene, 1,4-butanediol dimethacrylate, acrylonitrile, diphenyl
ether, or α-methylstyrene and acrylates.

[0096] The auxiliaries and additional substances mentioned can moreover be
added to the suspension. Amounts of from 3 to 15% by weight, based on the
entirety of monomer and TPU added. They can be added prior to, during or
after the polymerization of the suspension.

[0098] Before the TPU used is used in the polymerization it can be
processed via underwater pelletization to give mini pellets of average
diameter from 0.5 to 1,5 mm. The product obtained after the
polymerization reaction therefore has a particle size that can be
processed in conventional EPS machines. Amounts of from 0.01 to 15% by
weight of nucleating agents, such as talc powder or polyethylene waxes,
can moreover be incorporated by means of extrusion into the polyurethane
used.

[0099] One preferred embodiment of the process begins by using, as initial
charge, an aqueous phase which comprises from 0.1 to 10% by weight of the
abovementioned Pickering stabilizers, from 0.1 to 0.001% by weight of a
surfactant (for example sodium dodecylsulfonate), and from 1 to 90% by
weight of TPU pellets in a stirrable pressure autoclave.

[0100] The monomer, which optionally comprises the abovementioned
auxiliaries, such as initiators and flame retardants, is metered at room
temperature, or below the polymerization temperature, into the stirred
reactor. One variation of the process begins by combining the TPU at room
temperature with the monomer, which comprises the abovementioned
auxiliaries, such as initiators and optionally flame retardants, in the
absence of water, and allowing the material to swell for from 0.5 to 24
hours. The pellets swollen by monomer are then likewise transferred to
the polymerization reactor, which contains the aqueous phase with the
abovementioned Pickering stabilizer and with the surfactant.

[0101] It has proven advantageous to stir the reaction mixture for a
certain time (about 1 to 5 hours) at an elevated temperature below the
polymerization temperature (preferably from 10 to 60° C., for
example at 50° C.), in order to promote swelling of the TPU
pellets by the monomer mixture. The reaction mixture is then heated to
the polymerization temperature. Surprisingly, it has been found that
increased formation of the copolymer described above, made of TPU and
polystyrene, occurs at a preferred polymerization temperature of from 110
to 140° C. (use of a peroxide initiator with T1/2=1 h at from 120
to 135° C.).

[0102] The suspension polymerization reaction produces particles which are
bead-shaped and in essence round, with average diameter in the range from
0.5 to 4 mm if micropelletized TPU has been used, or particles of size
from 0.5 to 2 cm if no micropelletization of the TPU has been carried
out. They can be coated with the conventional coating agents, e.g. metal
stearates, glycerol esters, and fine-particle silicates. It has proven
particularly useful here to coat the polymer with from 0.1 to 1% by
weight of hydrophilic silica (Sipernat® FK320; Evonik).

[0103] The expandable-polymer-particle material can be processed to give
foams with densities of from 20 to 250 g/l, preferably from 50 to 100
g/l. For this, the preferred expandable-particle material is prefoamed
with steam (e.g. standard EPS prefoamer from Hirsch). The resultant
prefoamed particle material is preferably placed into storage for from 10
to 24 hours and then is preferably processed in a standard EPS machine to
give blocks or moldings.

[0104] For applications requiring high resilience with good recovery
capability (floorcoverings, solid-borne-sound-deadening), the resultant
blocks or moldings can be elastified by applying and removing load in
mechanical presses. Unidirectional elastification of the material has
proven to be advantageous here for these types of applications. In the
elastification process, a foam product (block or molding) is compressed
in a press to from 10 to 50% of its initial volume. Once the compression
process has ended, the compressed molding is placed into storage (for up
to 24 h) and is then appropriately cut to side. The elastified materials
have extremely high undirectional recovery capability.

[0105] The examples provide further explanation of the invention.

EXAMPLES

Precipitation of Magnesium Pyrophosphate (MPP)

[0106] An amorphous MPP precipitate was used as Pickering stabilizer in
all of the examples described. A decisive factor is that the MPP
precipitate used has been freshly prepared (at most 12 hours old), since
otherwise it is impossible to achieve adequate stabilization of the
reaction mixtures. The MPP precipitate can be used as follows:

[0107] 931.8 g of sodium pyrophosphate (Giulini) are dissolved in 32 l of
water at room temperature (25° C.). A solution of 1728 g of
magnesium sulfate heptahydrate (Epsom salt) is added, with stirring, to
this solution, and stirring is then continued for a further 5 minutes.
This gives a white suspension which settles after a few minutes. In the
examples described, the abovementioned suspension is used directly after
brief mixing/shaking.

TPU Pellets:

[0108] Commercially available polyether-based TPU is used (Elastollan®
1170AU, Elastollan® 1180A from BASF Polyurethanes GmbH). In order to
obtain expandable polymer pellets with a particle size typical of EPS
(from 0.5 to 4 mm), it has proven advantageous to use an extruder and
underwater pelletizer to convert the TPU into micropellets of particle
size from 0.5 to 2 mm.

[0109] It has moreover proven advantageous to incorporate from 0.1 to 1%
by weight of talc powder (Microtalc IT extra, Mondo Minerals) during
micropelletization. This ensures that a more homogeneous foam structure
is subsequently obtained (nucleating agent).

Inventive Example 1

1.1 Swelling

[0110] 3.00 kg of styrene in which 21.0 g of dicumyl peroxide
(Perkadox® BC-FF, AkzoNobel) had been dissolved were used as initial
charge in a 5 l stainless steel can (milk churn). 350 g of TPU
minipellets comprising 0.5% by weight of talc powder, Elastollan®
1170AU, were suspended in a sieve insert in the styrene solution for 4
hours. The sieve insert was then removed from the styrene-peroxide
solution, and the swollen material was allowed to drip dry for 5 minutes.
The mass of the swollen TPU pellets after drip-drying was 965 g, and they
were stored overnight (for about 10 h) in a PE canister.

1.2 Polymerization

[0111] The swollen TPU was transferred to a 6 l pressure autoclave [EPS
reactor, maximum pressure: 20 bar, blade stirrer; stirrer rotation rate
300 rpm] containing 3 kg of deionized water, 803 g of MPP precipitate,
and 42 g of 2% solution of E30 emulsifier (produced from E30-40 Leuna
Tenside GmbH). Once the reactor had been sealed and nitrogen had been
introduced (inertization) the system was heated within 1.5 hours to
125° C. One hour after 125° C. had been reached, 80 g of
isopentane were metered into the reactor within 40 minutes. The system
was kept at a temperature of 125° C. for a further 6.5 hours, and
then cooled to room temperature. The resultant polymer beads comprising
blowing agent were isolated by decanting, dried to remove inernal water,
and coated with 0.3% by weight of precipitated silica (Sipernat FK320,
Evonik). For equilibration purposes, the material was placed into storage
in a pressuretight container (zinc box) for at least 2 to 5 days.

[0112] Values determined on the resultant polymer after 5 days of storage
in a gastight container (zinc box) were: water (Fischer titration) and
volatiles content (gravimetric after 2 h at 120° C.):

[0113]
water content: 0.45%

[0114] volatiles content at 120° C., dried
for 2 h: 4.52%.

[0115] The nitrogen content of the polymer was determined (nitrogen
determination by Kjeldahl method). The TPU content of the polymer was
calculated by comparison with the TPU used

[0116] In order to assess expandability, foaming curves were generated in
a steam prefoamer at atmospheric pressure (Rauscher box, T=from
98-102° C.) after 5 days of storage in a gastight container (zinc
box). The bulk density of the prefoamed material was measured after a
defined prefoaming time.

[0117] After 5 days of storage in a gastight zinc box, the coated polymer
was prefoamed in a standard EPS prefoamer to a density of 50 g/l (steam
pressure 0.2 bar).

[0118] The prefoamed material was placed into storage for 10 hours and
processed in a standard EPS processing machine to give round moldings.
The following process parameters have proven to be practicable:

[0119] The resultant moldings were used for comparison of bending energy
in accordance with EN 12089 with expanded polypropylene (EPP) and with
expanded polystyrene (EPS) (Styropor, BASF SE). FIG. 3 depicts the
results.

Inventive Example 2

[0120] Inventive example 1 was repeated, except that TPU component used
comprised TPU minipellets with 0.5% by weight of talc powder made of
Elastollan 1180A (TPU based on MDI, polyTHF 1000, polyTHF 2000 and
butanediol) from BASF Polyurethanes GmbH.

Inventive Example 3

[0121] 10.5 g of dicumyl peroxide (Perkadox BC-FF, AkzoNobel) were
dissolved in 2.10 kg of styrene in a 5 l polyethylene canister, and 1.40
kg TPU minipellets comprising 0.5% by weight of talc powder (Elastollan
1170AU) were admixed. A shaker board was used to mix the mixture at room
temperature for 30 minutes.

[0122] The mixture was then transferred to a 10 l EPS reactor [pressure
autoclave (20 bar) with blade stirrer; stirrer rotation rate 300 rpm].
3.50 kg of deionized water, 1.07 kg of MPP precipitate, and 56 g of a 2%
solution of E30 emulsifier (alkanesulfonate, CAS 68188-18-1) (Leuna
Tenside GmbH) were used as initial charge in the reactor. The suspension
was heated to 50° C. within 30 minutes, and the temperature was
maintained at 50° C. for three hours for swelling purposes. The
temperature was then increased within one hour to 125° C., and 60
minutes after 125° C. had been reached 314 g of
pentane-S(Haltermann/Exxon) were then metered into the mixture within 60
minutes. The temperature of 125° C. was maintained for a further
5.5 hours, and then the reactor was cooled to room temperature. The
particulate polymers were worked up and processed by analogy with
inventive example 1.

Inventive Example 4

[0123] Inventive example 3 was repeated, but TPU used comprised grade
1170AU minipellets with 0.5% by weight of talc powder.

Application Example 1

Expansion Performance of Materials from Inventive Examples 1 and 2

[0124] 4 g of polymer from inventive example 1 or 2 was charged to
injection bottles (Max Wiegand, size 75×23 mm, item No.: 4382602)
sealable by rubber septum, and sealed. After a defined storage time, the
ampoules were opened and the material was prefoamed in a standard
Styropor prefoamer at atmospheric pressure (steam-treatment time 300 s).
The bulk density of the loose material was then determined
volumetrically.

[0125] The material from inventive example 2 can be prefoamed to a density
of 94 g/l after 19 days of storage, while the material from inventive
example 1 can be prefoamed to a density of 64 g/l even after 53 days of
storage.

Application Example 2

[0126] In a procedure similar to that described for inventive example 1,
0.3% by weight of Lumogen Red was admixed with the styrene used for the
swelling process. The foam obtained after processing had a red color.

Application Example 3

[0127] In a procedure similar to that described for inventive example 1,
0.3% by weight of Lumogen Green was admixed with the styrene used for the
swelling process. The foam obtained after processing had a green color.

Comparative Example 1

[0128] Inventive example 1 was repeated with the following alterations.
The polymerization process 1.2 used 965 g of straight TPU micropellets
instead of a styrene-saturated TPU. The resultant TPU-particle material
comprising blowing agent could not then be prefoamed to give expandable
foam particles.

Patent applications by Bernhard Schmied, Frankenthal DE

Patent applications by Frank Braun, Ludwigshafen DE

Patent applications by Frank Prissok, Lemforde DE

Patent applications by Klaus Hahn, Kirchheim DE

Patent applications by Patrick Spies, Neustadt DE

Patent applications by Peter Gutmann, Karlsruhe DE

Patent applications by BASF SE

Patent applications in class Expandible system contains two or more solid polymers or at least one solid polymer and at least one polymer-forming system

Patent applications in all subclasses Expandible system contains two or more solid polymers or at least one solid polymer and at least one polymer-forming system